Dipg-09. Prognostic Factors in Reirradiated Diffuse Intrinsic Pontine Glioma: Clinical and Radiomic Analysis

Abstract BACKGROUND Diffuse Intrinsic Pontine Glioma (DIPG) is a lethal pediatric brain tumor. Radiation therapy (RT) is the standard treatment, with reirradiation considered at progression. However, the prognostic factors for reirradiation remain unclear. This study aims to investigate the outcomes of patients with DIPG undergoing reirradiation and to identify radiomic prognostic factors. METHODS We analyzed patients with histopathologically proven DIPG who underwent reirradiation at our institution. We delineated pre-reirradiation tumors using 3D Slicer software and extracted radiomic features from FLAIR MRI sequences using the Python package PyRadiomics. Finally, we used the least absolute shrinkage and selection operator (Lasso) for Cox’s proportional hazard model with leave-one-out cross-validation to select optimal prognostic factors for survival after reirradiation. We have also compared the reirradiated group with our cohort of 22 non-reirradiated DIPG patients eligible for reirradiation but whose parents chose only supportive care at progression. RESULTS The study included 15 patients who received reirradiation at the first progression, with a total dose of 20 Gy or 24 Gy in 2 Gy fractions. Reirradiation was well tolerated, without grade 2 toxicity. Neurological improvement was observed in 80% of patients. Median survival from the end of the first RT was significantly (p = 0.01) longer in the reirradiated group (68 weeks) compared to the non-reirradiated group (25 weeks). The Cox model demonstrated a concordance of 0.88 (95% CI: 0.83–0.92), revealing that tumor sphericity and structural gray-level heterogeneity in FLAIR MRI images were associated with more prolonged survival in reirradiated patients. CONCLUSIONS Reirradiation is a safe and effective approach for patients with DIPG. MRI-based radiomic models could help predict survival after treatment. Our results revealed that tumors with low sphericity and high homogeneity of gray levels are associated with a worse prognosis after reirradiation.